Feature Request: Allow to use a new request in before-try event handler

[IanSun]

Currently, before-try event provides a Request object and use that object to make a request. It's impossible to modify the body and the query of the request for now because of these properties are read only.

Background is, I want to make a request with arbitrary query strings. This hasn't been supported by current spec. I tried to set the parameter key to an empty string according to this comment. RapiDoc renders well. However, it stills prepend the = symbol when I click "Try". I know that is a correct behaviour but what I hope is to provide a way to modify the url to meet my design.